3d printing using spiral buildup and high viscosity build materials

ABSTRACT

A 3D printing system utilizes a circular-shaped build area revolving symmetrically around a single center point in a continuous helical printing process. A viscous, solidifyable liquid composition is deposited on a construction area where it is exposed to a solidifying medium to form a physical object that is attached to a build platform above and parallel to the construction zone. The build platform continuously rotates and simultaneously rises in a gradual programmed manner to continuously produce adhered layers of material deposited and bonded in a helical fashion. The construction area includes mechanisms to continuously remove therefrom excess build material not incorporated in the physical object formed.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-part of U.S. patent application Ser. No. 15/088,365 filed Apr. 1, 2016, now U.S. Pat. No. ______, which is a Divisional of Ser. No. 14/207,353 filed Mar. 12, 2014, now U.S. Pat. No. 9,321,215, which claims the benefit of U.S. Provisional Application Ser. No. 61/778,285 to Kurt Dudley, entitled 3D PRINTING USING SPIRAL BUILDUP, filed on Mar. 12, 2013. This application also claims benefit of US Provisional applications 62/448,900 and 62/448,914, both filed Jan. 20, 2017, and 62/472,406 filed Mar. 16, 2017. These applications are hereby incorporated herein in their entirety by reference, including, but not limited to, the drawings, charts, schematics, diagrams and related written description.

BACKGROUND OF THE INVENTION Field of the Invention

Described herein are methods, procedures and devices for forming three-dimensional (3D) objects from a wide variety of media, such as a polymeric, biological or metallic materials. The methods, procedures and devices are programmed to produce desired three dimensional (3D) structures using polymerization, crosslinking, curing, sintering, melting or solidification and similar techniques in a manner constituting improvements over conventional stereolithographic, photocurable, or other 3D object forming techniques.

Description of the Related Art

In recent years, 3D printing has been demonstrated to be an effective technique for accurately forming 3D objects, such as for the purpose of prototyping and manufacture. In its most general sense, 3D printing typically utilizes a 3D scanner and/or computer software to generate an image map of a desired object. That image map is then translated into a grid-like structure such that a fabrication device can deposit a flowable material, such as a plastic, polymer, biomaterial or resin, via an additive process, which is simultaneously solidified creating a 3D object. Various existing 3D printing methodologies which provide unique advantages and also each have their own disadvantages.

One such methodology is stereolithography, credited as being developed by Charles W. Hull and set forth, for example, in U.S. Pat. No. 4,575,330. Stereolithography aims to create three-dimensional objects based on the successive linear formation of layers of a fluid-like medium adjacent to previously formed layers of medium and the selective solidification of those layers according to cross-sectional data representing successive slices of the desired three-dimensional object in order to form solid layers. Stereolithography technology uses a liquid medium that is typically a melted thermoplastic or a photopolymer which is selectively solidified. The thermoplastic solidifies by exposure to a lower temperature; the photopolymer is solidified by exposing it to radiation usually in the UV or visible wavelengths causing the polymer to crosslink or cure. Typical methods for directing this radiation onto photocurable materials include motor controlled scanning mirrors, mask systems or lasers wherein the smallest physical resolution is the size of the laser beam or, within the mask, the size of a pixel.

Stereolithography-based machines solidifying photopolymer-based resins typically utilize a singular, focused laser point which is scanned in the X-Y plane using a physical gantry system or is otherwise directed by electromechanically-driven highly reflective surfaces such as galvanometers or rotating polygon mirrors. Because of this, print speed is inversely proportional to both layer density and layer volume.

A method of using the “singular point” type of stereolithography to solidify photopolymers includes utilizing a laser and controllable mirror configuration is described in U.S. Pat. No. 4,575,330 to Hull. The process utilizes incrementally submerging a build-platform in a vat of photocurable material, wherein a layer of material that covers the build platform is solidified via targeted radiation from a laser using two controllable mirrors which direct the radiation in a x/y plane along the surface of the material. Areas are selectively solidified corresponding to cross-sectional data represented in a cross-sectional bitmap image of a slice of a virtual three-dimensional model representing an object. Lines are traced over the liquid surface to solidify the photocurable material. The process is repeated multiple times by lowering the build platform into the vat of material by an amount correlating to the next desired layer height. After new material is deposited over the construction area, the process of solidification repeats to form the individual stacked layers to form a three dimensional object.

Another method, which utilizes a “plane exposure” type stereolithography, is the use of a Digital Micromirror Device (DMD)-based variation on the stereolithography process. These variations provide significant improvements in print speed and create a constant build time independent of layer density for a given layer volume, because DMD arrays can expose and direct entire planes of focused light at once rather than a singular point which must be scanned to create a layer. A typical 720×480 DMD array can expose 345,600 individual “pockets” of solidified resin, also known as voxels, all at once in a single layer exposure. Typical layer exposure times can range from 0.2-10+ seconds, depending on a variety of factors. DMD-based processes can work very well for small print sizes, but once a critical layer area is surpassed, the suction force generated by layer-peeling mechanism will inhibit buildup of the 3D object.

There are several limitations to the above processes. For example, resolution is proportional to the focusable point size of the laser; if it is desired to increase the resolution, a smaller point size must be used. This has the consequence of increasing the total amount of lines to be traced in a given area, resulting in longer construction times. Additionally, the process of submerging a platform in a vat of material is both limiting to the functional size of the object that can be created and also requires exposure of large volumes of photocurable materials to construct the 3D object.

Furthermore, the above method of subjecting a fluid surface to radiation poses its own set of issues with regards to consistent layer heights and errors that can be caused from disturbances to the liquid surface. These disturbances can result from both internal and external sources of vibration. The layer height, and therefore the vertical resolution of the object, is also dependent on the viscosity and surface tension of the material used. This limits the vertical resolution that is attainable with a given range of materials.

Recently, an inverted sterolithographic process has been developed that introduces the additional factor of surface adhesion resulting from a newly solidified layer adhering to the bottom of a vat. This adhesion force increases as a function of the size of the solidified layer. However, before the construction process can resume, the adhesion force must be removed and the build platform raised to allow new material to be placed prior to the solidification of the next additional layers of material, for example, via use of prying, tilting, peeling and sliding.

These processes for removal of the adhesion force place the vat, the build platform, the raising element for the build platform and the newly solidified geometries of the printed object under high stress loads that can decrease the functional life of the machine and its components, as well as causing deformations and delamination of the object being constructed. A method to reduce this surface adhesion in large area solidification is described in European patent application EP 2419258 A2, where a single layer is broken into sub component images that are solidified and separated individually. This method, however, doubles the construction time and increases the chance for product failure due to delamination caused by increasing the amount of unsupported areas to be solidified.

Common areas where all rapid manufacturing systems can be improved upon comprise increasing resolution, enhancing scalability of constructible parts, increasing the ability to construct difficult geometries, such as hollow cavities and overhangs, and increasing the ability to construct and preserve small and fragile geometries, such as those having little surrounding support. Time to construct individual layers and total construction time are other important factors relating to the efficiency of the construction process of every system each of which has its own set of unique limiting factors that dictate how long it will take to construct a given object. Efficient methods and devices that address these conventional inefficiencies while utilizing a single compact device is therefore needed.

SUMMARY

Described herein are methods, devices and systems for efficient 3D printing that address inefficiencies and deficiencies of currently existing 3D printing systems utilizing a single device. For ease of explanation and to provide an efficient nomenclature, the formation of 3D structures using the new techniques, procedures and devices set forth and incorporating features of the present invention are referred to as Heliolithography™. Heliolithography™ provides solutions to the above mentioned inherent problems associated with traditional prototyping techniques. It allows 3-dimensional solid physical products to be made directly from computer-driven data and reproduced with very high and accurate levels of detail, in a short time using a completely automated process. Certain aspects of Heliolithography™ are similar to stereolithography. Both Heliolithography™-based and stereolithography-based processes can utilize a variety of materials as their base material, and these materials are solidified into physical parts through various solidification techniques, such as a free radical polymerization of photopolymers upon exposure to a precisely directed and focused actinic photon source of sufficient energy density. However, there are several key differences between Heliolithography™ and stereolithography-based printing processes.

Heliolithography™ utilizes the best of “singular point” and “plane exposure” concepts discussed above to continuously solidify the building material, such as a photopolymer material, in thin lines by a spiral buildup. When these lines are oriented as radii in a build area, for example, in a circular-shaped build area revolving symmetrically around a single center point, then a continuous printing process can be performed in a helical fashion. The build platform (upon which solidified material is deposited to form the physical object) in one embodiment is continually rotated and simultaneously raised in a very gradual manner while the material to be solidified, such as a photopolymer is deposited as a liquid in a thin line on a transparent platform. A stationary line of focused actinic radiation delivered from a position below the platform is directed into the liquid photopolymer to produce a single continuous “layer” of the now solidified material deposited and bonded to adjacent previously or simultaneously deposited material in a helical fashion. Alternatively, Heliolithography™ can also be implemented by slowly raising the build platform without rotation while a line of focused radiation “spins” beneath in a programmed manner, curing liquid photopolymer continuously. In a further embodiment, the platform can be periodically or continuously rotated and at the same time the actinic light can be periodically or continuously reposition during the buildup and curing process.

Methods and systems incorporating features of the present invention seek to solve the issue of having both simultaneously high construction resolutions while still preserving the ability to print large structural objects in a faster more economical way than can be achieved by the prior art. Such systems can utilize a continuous method for depositing and solidifying materials, for example, photocurable materials, in a rotational manner that results in a spiral build-up of material.

In some embodiments of an apparatus incorporating features of the present invention, a rotating build platform with an elevation that can be controlled along a Z-axis is utilized. This build platform is lowered onto at least one solidification area which comprises at least one material dispenser, at least one transparent substrate, for example, from which a material flows and is held against the build platform during solidification, at least one drainage system to remove unused material and at least one excess material stripper for collecting and removal and recycling of unsolidified excess materials. In a photopolymerization process, electromagnetic radiation emitted from a source below the transparent substrate, is directed onto the photocurable construction material in specifically targeted regions that coincide with point data derived from a three-dimensional object that is stored in the machines memory system.

In the use of photopolymers, both construction materials and irradiation sources are selected to provide a near instantaneous cure of the construction material. The solidified material adheres to the rotating build platform, resulting in the continuous or semi-continuous spiral build-up of material to construct an object substantially similar in appearance to a desired three-dimensional object. In utilizing these processes incorporating features of the present invention, vertical resolution of a constructible object can correspond to the layer height or layer pitch angle of a continuous spiral layer of material and can be controlled by altering the relative distance at which the inverted build platform is suspended above the photocurable material that is held on a transparent substrate.

These and other further embodiments, features and advantages of the invention would be apparent to those skilled in the art based on the following detailed description, taken together with the accompanying drawings, in which:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional exploded view of a 3D printer device incorporating features of the present invention;

FIG. 2 is a front perspective view of the 3D printing device of FIG. 1 incorporating features of the present invention.

FIG. 3 is a cross-sectional exploded view of components of a 3D printer device incorporating features of the present invention;

FIG. 4 is a perspective view of an imaging component of a 3D printer incorporating features of the present invention;

FIG. 5 is a perspective view of a z-axis elevator stage of a 3D printer incorporating features of the present invention;

FIG. 6 is a perspective view of a build platform attachment plate for a 3D printer incorporating features of the present invention;

FIG. 7 is a perspective view of a removable build platform insert for a 3D printer incorporating features of the present invention;

FIG. 8 is a bottom view of a removable build platform insert for a 3D printer incorporating features of the present invention;

FIG. 9 is a top view of a view of an expanded solidification area/vat for a 3D printer incorporating features of the present invention;

FIG. 10 is a partial internal perspective view of a base material storage and construction area of a 3D printer incorporating features of the present invention;

FIG. 11 is a perspective view of a complete solidification area of a 3D printer incorporating features of the present invention;

FIG. 12A depicts a single item being constructed radiating from the center of the build chamber floor of a 3D printer component incorporating features of the present invention;

FIG. 12B depicts multiple items under construction radiating from the center of the build chamber floor of a 3D printer incorporating features of the present invention;

FIG. 13A is a side view of a continuous spiral layer construction utilizing a single construction buildup area of a 3D printer incorporating features of the present invention;

FIG. 13B is a side view of a continuous spiral layer construction buildup utilizing multiple construction areas of a 3D printer incorporating features of the present invention;

FIG. 14 is a perspective view of a radiation source for a 3D printer component incorporating features of the present invention;

FIG. 15 is a perspective view of an alternative radiation source for a 3D printer incorporating features of the present invention;

FIG. 16 is an expanded perspective view of another radiation source for a 3D printer incorporating features of the present invention;

FIG. 17 is a perspective view of a fourth radiation source for a 3D printer incorporating features of the present invention;

FIG. 18 is a perspective view of a fifth radiation source for a 3D printer incorporating features of the present invention;

FIG. 19 is a process flow diagram for a specific embodiment for a product buildup using the 3D printer device shown and described herein;

FIG. 20 is a process flow diagram for a specific embodiment for a product buildup using the 3D printer device shown and described herein;

FIG. 21 is a process flow diagram for a specific embodiment for a product buildup using the 3D printer device shown and described herein; and

FIG. 22 is a side view of the 3D printer device of FIG. 1, with a 3D structure in the process of being printed.

FIG. 23 shows a first embodiment of a reservoir/cartridge system for delivering a viscous material

FIG. 24 shows a second embodiment of a reservoir/cartridge system for delivering a viscous material

FIG. 25 shows an alternative embodiment of a material dispensing system which includes a mechanism for removal of excess, uncured build material.

FIG. 26 is an enlarged view of a portion of FIG. 25.

FIG. 27 is a top view and FIG. 28 a perspective top view of an alternative means to feed viscous build material to the build and curing portion of a 3D printing system.

FIG. 29 shows a further embodiment of a build platform and build plate mounted on the bottom of a rotational platform which is in turn mounted on a multi-axis Z height robotic arm.

DETAILED DESCRIPTION

The present disclosure sets forth methods and devices for efficient 3D printing that address conventional inefficiencies and deficiencies while utilizing a single compact device. As illustrative of such methods and 3D production devices, the dispensing of a photocurable substance onto transparent substrate, the selective curing and solidified of such materials and the retrieval of the solidified product is described. However, one skilled in the art, based on the teachings herein, will recognize that the apparatus and techniques described herein are not limited to the use of photopolymers along with the irradiation sources suitable to effect solidification, but can be readily adaptable to a broad range of flowable materials that can be rapidly solidified for the continuous formation of solid, three dimensional objects.

Throughout this disclosure, the preferred embodiments herein and examples illustrated are provided as exemplars, rather than as limitations on the scope of the present disclosure. As used herein, the terms “invention,” “method,” “system,” “present method,” “present system” or “present invention” refers to any one of the embodiments incorporating features of the invention described herein, and any equivalents. Furthermore, reference to various feature(s) of the “invention,” “method,” “system,” “present method,” “present system,” or “present invention” throughout this document does not mean that all claimed embodiments or methods must include the referenced feature(s).

It is also understood that when an element or feature is referred to as being “on” or “adjacent” another element or feature, it can be directly on or adjacent the other element or feature or intervening elements or features that may also be present. Furthermore, relative terms such as “outer”, “above”, “lower”, “below”, and similar terms, may be used herein to describe a relationship of one feature to another. It is understood that these terms are intended to encompass different orientations in addition to the orientation depicted in the figures.

Although the terms first, second, etc. may be used herein to describe various elements or components, these elements or components should not be limited by these terms. These terms are only used to distinguish one element or component from another element or component. Thus, a first element or component discussed below could be termed a second element or component without departing from the teachings of the present invention. As used herein, the term “and/or” includes any and all combinations of one or more of the associated list items.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. For example, when the present specification refers to “a” source of radiation or “a” material it is understood that this language, in the first instance, encompasses a single source or a plurality or array of radiation sources and, in the second instance, a single or multiple sources of materials. It will be further understood that the terms “comprises,” “comprising,” “includes” and/or “including when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

It should be further recognized that reference to “solid” 3D structures refers to the materials of construction becoming solid and that the 3D product produced is not necessarily a solid structure and may include products with unfilled or hollow spaces therein or, if intended, an open, porous or lattice-like structure and may in fact include spaces therein enclosing a liquid or non-solid filling material.

For the purpose of describing the construction procedure, the term “inverted” or “inverted build” refers to the method and procedure of building a 3D structure which is suspended below a horizontal assembled build structure 16, 18 with a portion sometimes referred to as the “base” of the 3D structure attached to the build platform insert 18. The assembled build structure 16, 18 rises vertically from and above the construction/solidification area 20, as it prints a 3D structure 780 such as shown in FIG. 22.

In some embodiments, the basic essential functionality of the Heliolithography process can be carried out through the use of 3D model software files, which produces an image map that is sectionalized into a spiral or helical structures using computer assisted drawing (CAD)-type computer programs. The spiral structure can be converted into segmented images or bit data corresponding to points along the surface areas of the intended printed object that are to be solidified by the controllable projection of radiation onto exposed areas to selectively solidify the materials of construction.

The solidification method can utilize any build material capable of changing from a liquid or flowable state to a solid in response to a stimulus. For example, solidification can be the result of providing a radiative source which has the appropriate physical characteristics to cure or react the irradiated reactive liquid photopolymer material positioned on the rotating build platform. In some embodiments, the build material comprises a photopolymer solution containing at least one photoinitator. The photoinitator absorbs radiation at specific wavelengths producing free radicals which cause the rapid polymerization in the localized irradiated regions. Representative chemistries that can be used can comprise unsaturated polyesters, styrene-Polyenes, Thiols-Acrylates, and methacrylates-Cycloaliphatic epoxides. Alternatively, a second reactive material can be dispensed to cause a crosslinking of a primary polymer. Further, thermoplastics can be heated to liquefy and then rapidly cooled to solidify. As a still further alternative powdered metals or thermoplastics can be dispensed and “spot welded” using a heat source or laser beam.

A typical formulation for a photoreactive material used in such a process comprises one or more monomers (molecules of low molecular weight that provide the specific desired properties and adhesion), Oligomers (medium length polymer chains that contribute additional properties such as increased tensile strength, stiffness, and elongation), photoinitiators (light sensitive materials that trigger free radical production to initiate the polymerization process), and additives such as fillers, pigments, dyes, adhesion promoters, abrasion resistant materials, UV light stabilizers and chemical stabilizers.

One example of a photopolymer formulation that can be used in the process described comprises a solution of monomer such as 1,6-Hexanediol (HOCH₂(CH₂)₄CH₂OH) and Polyethylene Glycol Diacrylate (C₃H₃O).(C₂H₄O)_(n).(C₃H₃O₂) with one or more photoinitators, phenylbis(2,4,6-trimethylbenzoyl)-phosphine oxide [CH₃)3C₆H₂CO]2P(O)C₆H₅ and Diphenyl(2,4,6 trimethyl benzoyl) phosphine oxide (CH₃) 3C₆H₂COP(O) (C₆H₅)₂ at concentrations between 2 and 8 percent by weight.

FIGS. 1-2 show a sectional and front perspective views respectively, of some of the major functional components of an example 3D printer 10 incorporating features of the present invention. The 3D printer 10 comprises an imaging unit 12, a z-axis elevator stage 14, also referred to as the construction frame, a build platform 16, and a build platform insert 18 which is configured to fit together with the build platform 16, to provide an assembled build platform (as shown in FIG. 2). Although the present disclosure sets forth a configuration utilizing both a build platform 16 and a build platform insert 18, it is understood that the use of the methods and devices incorporating features of the present invention can utilize the build platform 16 alone without the build platform insert 18. Below the assembled build platform 16, 18 is a construction/solidification area 20, a material storage area 22, a material cartridge/reservoir 24, electronic components 26, and a solidification mechanism 28. These components and their various sub components are discussed in greater detail throughout the present disclosure.

With reference to FIGS. 1 and 2, a 3D file (corresponding to a desired 3D object to be produced (the “print task”)) is loaded into the memory of a print processor 100, which is configured to operate in conjunction with a CPU and solid state memory storage, to control the 3D printer 10. This print task can be transferred through the CPU and into solid state storage in a variety of ways know in the art. For example, it can be transferred from a remote server or program using internet protocol (through its Ethernet or WiFi connection 102), or it can be loaded manually by the user using a control interface 104 and/or universal serial bus (USB) data transfer ports. Control interface 104 can be any control interface known in the art. In the embodiment shown, control interface 104 is a touch screen interface, such as an LCD touch screen interface. The data can be uploaded to the apparatus which performs self-tests and priming functions to ready the machine for printing. Motor drivers 108, work in conjunction with the print processor by receiving low-voltage signals from the print processor 100 and generating controlled current signals needed to properly drive the various motors used throughout the printer. Other electronics within the electronics component assembly 26 of the 3D printer 10 include a power supply 112, which can transform voltage input to provide regulated power to all the components of the electronic component assembly 26. It is understood that while the power supply 112 is depicted as comprising an outlet, any suitable power supply known in the art, for example, battery- or generator-based power supplies, are within the scope of the present disclosure.

The printer comprises a build platform 16 and a construction area 20. Build platform 16 can be permanently installed or replaceable, e.g. being removable connected to z-axis elevator stage 14. The build platform 16 can be rotatable clockwise and/or counterclockwise or otherwise moveable in one or more directions and can have a variety of shapes including any regular or irregular polygon or can be circular or substantially circular. The build platform 16 can be lowered towards the solidification area 20 using z-axis stepper motors 114; a sensor 124 can be used to determine when the desired layer-height of an object to be produced has been reached. The printer will then begin the print cycle by first ensuring all moveable axes are in the correct starting position. For the z-axis, the starting position is typically one layer height above the cure zone (above the home position). However, it is understood that other starting positions can be designated as needed for a particular print task and/or as newer technology becomes available and is incorporated into devices and methods according to the present invention. For the rotation axis, the starting position is the same as the home position.

The homing process, which establishes the ‘0’, or start position of each axis, uses sensors 124, such as hall effect sensors, in a closed-feedback system to determine the hard limits of each axis. Hall effect sensors are known in the art and typically comprise a transducer that varies its output voltage in response to a magnetic field. Hard limits for each axis can be driven from a pair of linear sensors, such as hall effect proximity sensors 124, positioned at each limit. When utilizing hall effect sensors, one or more small magnets 126 can be embedded in the moveable z-axis carriage 14. Because the sensors have a linear analog output directly proportional to magnetic flux, each sensor can be calibrated with its own trigger voltage.

Once hard limits are determined, printer firmware maintains in its memory the current position of each axis relative to its home position. When the printer is powered on, it can be programmed to re-home each axis before accepting new print tasks, for example, to compensate for situations wherein an axis has been moved while the printer was powered off. The current position of each axis can be stored as an integer number of motor steps from zero. In these configurations, moving the axis “up” will increase this internal counter, and moving the axis downwards will decrease the counter.

Soft limits can also be put in place to configure the printer such that the printer will never allow a motor movement that will send the axis below the lowest position or past the maximum allowed value, which is specific to each axis' length. If an axis is directed to exceed these preset limits the printer controller will halt the print task and issue an appropriate error message. Also, if there is ever a programming error and the printer attempts to move past the soft limit, the hard limits built into each axis will halt the axis movement and the print task before any damage to the printer occurs, requiring entry of an appropriate soft reset.

The material storage area 22 can hold a replaceable material cartridge 24. The material cartridge contains electronically stored information which can be read by the 3D printer 10 to determine the amount of material in the cartridge 24 and other specifics about the material in the cartridge. An agitator mechanism, such as a magnetic stirring device 230, as shown in FIG. 10, can also be included and be located below the cartridge 24 to ensure materials are uniformly mixed prior to dispensing. One or more atmospheric control mechanisms 119, such as an electronic heating mechanism and/or a fan and/or humidifying control systems can also be used to alter the temperature of construction material in the material cartridge 24 or control the exposure to moisture if needed, for example, to reach a desired viscosity or reduce detrimental moisture prior to dispensing. A thermal sensor and/or humidity sensor can also be used to monitor when a desired material temperature is reached or that no excess moisture is present.

Referring to FIG. 10 a material pump 115 can be used to move photocurable build materials, such as liquid-state photocurable materials, from the material reservoir 24 to a material depositor. At least a minimal amount of material needed for a proper thickness coating on the build surface can then be dispensed. A material such as photopolymer resin can be introduced to the print area by the printer's internal plumbing system, driven by a small pump. With reference to FIG. 10, as resin is introduced, it flows down resin supply channels in a print head and flows over the cure zone and into resin return channels 117. Excess liquid resin is continuously pulled from the resin return channels 117, filtered and returned to the resin tank or discarded, if appropriate.

The assembled build platform 16, 18 can then be rotated, which spreads liquid resin over the solidification area, depositing and evenly spreading the photopolymer to a desired layer thickness. In some embodiments, the desired thickness is between 0.001 mm and 0.1 mm in thickness. A secondary material dispenser can optionally be used to infuse the primary material with additional additives, pigments, dyes, coloring agents into the primary photopolymer prior to curing. In an alternative embodiment, the secondary material can be a material reactive with the first material to effect solidification. It is understood that while the embodiments described herein set forth a rotatable build platform and stationary material dispensers and solidification areas, the reverse configuration would also work and be within the scope of the present application, wherein material dispensers and soldifcation areas rotate under stationary build platform. In an alternative embodiment, the material dispenser, solidification and build platform can be simultaneously or alternatively moved in a programmed manner.

Once a continuous resin flow is established, the assembled build platform 16, 18 begins to rotate before the solidification process begins to establish a uniform flow of material across a material spreader. The rotation of the assembled build platform 16, 18 is performed with the use of a variable speed motor 136 that drives a central shaft 137 with engaged 90 degree gears 138 that rotate both the scanner and assembled build platform 16, that are suspended on one or more bearings 142 connected to the z-stage 14. The build platform can be set to spin for set number of rotations, also known as the “spin-up” period. The rotation of the assembled build platform 16, 18 helps to draw new material over the cure zone and ensures that no air is trapped. Without pausing rotation, the printer begins the printing process by activating the solidification mechanism to begin the photo-cure process.

Continued rotation of the build surface (or movement of the feed mechanisms or other components programmed to move) advances the print materials onto an across an exposure/cure zone 118, which is preferably glass or another sturdy, transparent and preferably low adhesion medium. The exposure zone 118 can be treated with a non-stick and abrasion resistant coating, which prevents or retards cured material from adhering to its surface. Selective solidification of the segment of material deposited between the build platform and the transparent construction surface, is carried out by one of a number of possible combinations of radiation sources and radiation directing mechanisms used to direct the radiation through the transparent substrate portion of the solidification area onto and into the liquid construction materials. Material level sensors in the material cartridge 24 are also used to monitor material levels and are capable of pausing or slowing a print cycle if material levels become critically low.

The data stored in the memory of the printer is transmitted to the solidification mechanisms 28 in a programmed manner to selectively expose portions of the photopolymers through the transparent substrate, which are solidified in a manner corresponding to the structural information relating to specific segments of the 3D model which is being constructed. The Heliolithography™ process, which appears to be continuous can actually comprise many small cumulative “steps” for each full rotation of the build platform, pausing at each step for a small amount of time, typically between 5-10 milliseconds required to allow the polymerization reaction to progress past a critical “degree of cure” (i.e., a level of solidification) needed to sufficiently attach to the build platform insert 18 and firmly to adjacent previously solidified portions of structure being formed. As an alternative the build platform insert 18 can comprise a removable retention means added to the lower surface thereof which can be incorporated onto the first layers of the product being built so as to allow removable attachment of that structure, once completed, from the build platform insert. In some embodiments, referring to FIG. 8, the holes can be shaped to add alternative retention structures 770 such as inverted cones or additional structures 770 can be added to provide further retention of the structure being built. Unsolidified material is simultaneously removed and recycled back into the reservoir.

As the portion of the structure being built is sufficiently solidified, the rotating assembled build platform 16, 18 continuously removes the solidified material from the exposure zone 118 and provides new construction material spreading across the construction area 20. Solidified material is also, at the same time, rotated towards a recycling area comprising a drain 132, such as an excess materials stripper, that removes any unsolidified materials from the growing structure which are then filtered and recycled back into the construction materials reservoir 24, and a further curing mechanism 133, if necessary.

As each additional step of the build process is reached, new information is provided to the curing mechanism 133, so as to solidify the resin where and when needed. As the assembled build platform 16, 18 rotates, it is continually raised by the linear actuators in a ratio such that the assembled platform 16, 18 is raised one layer height for each revolution. In some embodiments, one layer height corresponds to the number of radii of an intended curing piece of the structure. For example, in embodiments utilizing one material while curing down the diameter (i.e. 2 radii) a full layer would be cured during every 180 degree rotation of the build platform. In some embodiments utilizing multiple cure areas, but still utilizing a single material, a single layer can be cured faster with less rotation, for example, at approximately 360 degrees/number of cure radii. The linear actuators include stepper motors 146 that are coupled via coupling devices 148 to fasteners, such as lead screws 150, so as to raise the z-stage which is connected with fastener acceptor, such as a lead screw nut 152, when rotated. Bearings 154 and linear guide rails 156 mounted in the z-stage 14 stabilize this vertical movement.

This cycle is repeated until the spirally deposited and solidified material is built up and the constructed three-dimensional object suspended below the assembled build platform 16, 18 but above the construction/solidification surface 20 is completed. This process is repeated in a continuous fashion until, cumulatively, the total height of the printed object has been reached. Once this is accomplished and the cure mechanism has no remaining information in its input buffer, the curing mechanism (the photon source) is shut off and the rotation of the build platform is stopped. The resin flow is shut off and all remaining liquid resin drains back into the material cartridge. The machine initiates a motion sequence raising the build platform to its upper soft limit and brings the rotation of the platform to its homed ‘0’ position.

In addition to utilizing preexisting software print modules, methods and devices incorporating features of the present invention can also utilize scanning and other imaging units. In some embodiments, objects can be placed on a scanner platform 139 and the printer 10 can be instructed to begin scanning. The z-stage 14 raises the object to an initial height to begin a scan. A pattern imaging device 206, such as a projector, or laser can be used to project a known geometric pattern on the surface of the object. A recording device 208 can then record the distortions to this known geometric pattern as the scanner platform 139 rotates driven by the same variable speed motor 136 and drive gears 138 as the build platform. The height of the object can be raised or lowered using the linear actuators to perform subsequent passes to generate greater coverage of the object geometry to include under cuts and over hangs. This information is then sent to the processor 100 and transmitted via Ethernet, WiFi or wired connection 102 to a computer or cloud system for the reconstruction of the scanned object.

Many different solidification mechanisms can be utilized with methods and devices according to the present disclosure. A solidification mechanism 28 used in the device of FIG. 1 can include any radiation source such as high power diodes 212, 214, with the radiation directed through correcting and focusing optics 222 and onto a motor controlled mirror scanning system 220 for directing the radiation through the exposure zone 118 of the cure zone. Other solidification mechanisms are discussed further below.

FIG. 3 shows an exploded view of an imaging unit 12, a z-axis elevator stage 14, a build platform 16, a build platform insert 18 which is configured to fit together with the build platform 16 to form an assembled build platform 16, 18 (as shown in FIG. 2), a construction/solidification area 20, a material storage area 22, and a material cartridge/reservoir 24. FIG. 3 shows these components aligned in correct configuration according to some embodiments incorporating features of the present invention, such as the embodiment 10 depicted in FIGS. 1-2 of the present application. FIG. 4 shows an enlarged view of the imaging unit 12, which comprises a pattern imaging device 206 and a recording device 208 as discussed above. The imaging unit 12 can be connected to z-axis elevator stage 14 via bearings 154 as shown in FIG. 1.

FIG. 5 shows a more detailed view of z-axis elevator stage 14, which comprises magnets 126, which can interact with hall effect sensors to relay the position of the z-axis stage 14, a variable speed motor 136 that drives a central shaft 137 with engaged 90 degree gears 138, a scanner platform 139 and fastener acceptors 152. These components can function as set forth above.

FIG. 6 shows an enlarged view of the build platform 16. One aspect more clearly shown in FIG. 6 is the insert accepting portion 224. FIG. 7 shows the build platform insert 18 and the inset connecting portion 226. The insert accepting portion 224 of the build platform 16 as shown in FIG. 6 can be configured to interact or mate with the inset connecting portion 226 of build platform insert 18 shown in FIG. 7 such that the two components can be connected into an assembled build platform 16, 18 (as shown in FIG. 2, for example). This allows the build platform insert 18 to be readily removed and replaced in the device. FIG. 8 shows a bottom view of the build platform insert 18 comprising arrays of holes 228 allowing increased surface area for building materials. The removable build platform insert 18 or a removable attachment to the build platform insert 18 can be separated from the complete product or remain as a piece of the complete product.

FIG. 9 shows an enlarged view of the construction/solidification area 20, comprising a primary material dispenser 180, a cure zone 118 and resin return channels 117. FIG. 10 shows a material spreader 182, and a curing mechanism 133, such as an excess materials stripper, these components functioning as set forth above.

FIG. 10 shows an enlarged top perspective view of the material storage area 22 and the material cartridge reservoir 24. Also shown in FIG. 10 are the control interface 104, a material pump 115, resin return channels 117, an exposure/cure zone 118, which is a transparent substrate, an atmospheric control mechanisms 119, curing mechanisms 133, a coupling devices 148 attached to fasteners 150, linear guide rails 156 within the coupling devices, a primary material dispenser 180, a material spreader 182, a secondary material dispenser 184 and a magnetic stirring device 230. FIG. 10 also shows additive material cartridges 186 which can be configured to feed secondary material through a primary material dispenser 180 and/or a secondary material dispenser 184.

FIG. 11 shows a condensed perspective view of a construction zone 720, comprising primary material dispenser 180, a material spreader 182, a secondary material dispenser 184, an exposure/cure zone 118, which is a transparent substrate, resin return channels 117 and curing mechanisms 133. The same structures are shown in FIG. 12A which shows a single construction zone 720 radiating from the center of the floor of the build chamber 21. FIG. 12A also shows an additive material cartridge structure 186. FIG. 12B shows an alternate configuration, wherein multiple construction zones 720 and additive material cartridge structures 186 radiate from the center of the floor of the build chamber 21.

For illustrative purposes, FIGS. 13A and 13B are side views of a spiral layer printing construction for a single construction area 231 and for multiple construction areas 232, respectively. The use of multiple construction areas further provides the benefits of simultaneous layer creation or the expanded ability for a greater range of construction material options wherein each construction area can dispense and solidify a unique range of materials into a single layer. For depositing into a single construction layer the subsequent heights of the construction substrates can also match the pitch of the spiral layer to be created and insure consistent layer thickness at each construction area. However, this is not necessary to achieve the desired color accuracy. This process can also be utilized wherein the build platform is rotated but raised only after one complete rotation is accomplished. This is of particular value where multiple construction areas of the same height are used. In such instance a consistent layer height for each material segment can be efficiently achieved. In actual operation the depicted expanded spiral can never occur as proper solidification techniques adhere and solidify together adjacent subsequent layers of the spiral laydown as they are formed.

Various solidification mechanisms and radiative sources can be utilized with devices and methods incorporating features of the present invention. FIG. 14 shows the solidification mechanism 28 of FIG. 1. When a photopolymer is used solidification mechanisms 28 can include various radiation sources such as high power diodes, LEDs or lasers 212, 214. In a particular embodiment the radiation is directed through correcting and focusing optics 222 and onto a controlled scanning mirror system 220 adapted to scan the incident light such as by use of a motor drive for directing the radiation through the exposure zone 118. The solidification mechanisms 28 can further incorporate a DMD Chip Micro mirror device (not shown).

FIG. 15 depicts a solidification mechanism 235 utilizing a Microelectromechanical systems (MEMS) or light valve switches. Depicted are high power diodes 212, 214, similar to the diodes that can be utilized with solidification mechanisms 28 described above, coupled to light/wave guides 236 in an optics system 238 for focusing onto a light switch 240 assembly. The light switch 240 is a mechanism allowing radiation to pass through at desired locations arranged in an overlapping hexagonal grid system. Fans and heat sinks 242 and a TEC temperature control system 244 can also be utilized for temperature control.

FIG. 16 shows an alternative solidification mechanism comprising a board radiation source 246 such as an ultra-high performance (UHP) Mercury Vapor lamp 248. This mechanism uses a convex reflector 250 for focusing the radiation from the source 246 towards a digital mask 252 such as a LCD screen. The digital mask controls radiation passing through according to a pixel matrix programmed to block or transmit the radiation flowing there through.

FIG. 17 is a further alternative solidification mechanism using a radiation source 254 comprising a high power diode 246 and a motor controlled mirror, such as a polygonal multi-sided mirror 258. The mirror is rotated in relation to the diode, or vice versa, to scan the radiation in a linear direction corresponding to its angle of rotation. A 45 degree secondary mirror 260 is used to reflect the radiation towards an exposure zone such as the transparent substrate of the cure zone 118. This secondary mirror 260 can be motor controlled to provide a second dimension of scanning. An optics system 262 is also used to correct for distortions and scanning angles. In some embodiments, an F-theta optic system is utilized.

FIG. 18 shows further alternative solidification mechanism 264 comprising an array of individually addressable diodes 265 such as a micro-LED array 266, that can be used independently to control the solidification of the construction material. An optic system 268 can also be used to focus the radiation to a desired point size between 5 and 50 nm.

A still further alternative can be to use one or more laser beams, which may or may not require focusing mirrors, as the laser beams can be individually positioned or repositioned as necessary to deliver narrow, pin point beams of controlled frequency light to specific target locations.

With reference to FIG. 22 a specific product is constructed utilizing devices incorporating features of the invention. Using the scanning techniques described above, the dimensional features and surface characteristics of a three dimensional object measuring less than about 10.5 inches in diameter and less than about 9.25 inches tall were scanned and the scanned data relating thereto was stored in the memory of a 3D build system such as shown in FIGS. 1-2. A photo photopolymer, preferably an acrylate methacrylate resin comprising 2-8% of a combination of diphenyl (2,4,6 trimethyl benzoyl) phosphine oxide, Thermoplastic Polyolefin (TPO), and/or Phenylbis (2,4,6-trimethylbenzoyl) phosphine oxide, was added to the material storage area 22. A light source suitable to effectively cure the photopolymer within 3-10 cc/sec comprising an array of micro LED (365-385 nm) to provide irradiation of the polymer over at least about 10.5″ width or diameter (approximately 200-300 watts/cm²).

The polymer was metered at a rate of about 3-10 cc per second which is dependent on the dimensions of the object being built distributed onto a 12 inch diameter construction area (cure surface) with a transparent exposure zone, which can be a smaller portion of the construction area, for example, a linch wide portion that is transparent to a certain type of radiation, such as UV radiation, which can be made of glass. This exposure zone had been previously treated with a low adhesion material such as Fluorinated ethylene propylene (FEP) and/or Polytetrafluoroethylene (PTFE), known commercially as Teflon®, to retard or prevent adhesion of the cured polymer to the cure surface. The resultant liquid polymer film was about 20-100 microns thick. The rotation rate of the built platform is primarily dependent on size and density of the product being built and the solidification rate of the material of construction, which in turn is dependent on the intensity and frequency of the irradiation source. The platform was rotated at a rate of 2-12 rpm.

The speed of construction can be enhanced by use of multiple cure areas and multiple feeds. However, construction of a structure is dependent on the size of the structure and the thickness of build material that can be cured per exposure. A general equation for estimating build speed is as follows:

${{Build}\mspace{14mu} {Speed}} = {\frac{1}{\left( {{RPM}*{Number}\mspace{14mu} {of}\mspace{14mu} {Radii}} \right)} \times \frac{{TOTAL}\mspace{14mu} {HEIGHT}}{{LAYER}\mspace{14mu} {HEIGHT}}}$

Accordingly, for a structure with an intended height of 9 inches (228.9 millimeters) with a layer height of 50 microns (0.05 millimeters), a rotation speed of 5 RPM and a single cure zone, a build time is estimated to be approximately 915.60 minutes, which is approximately 15.26 hours ([⅕]*[228.9/0.05]). However, with four cure zones such as shown in FIG. 12B the build time is cut to 25% (approximately 3.8 hours). Depending on the build material additional cure zones can be added to further reduce the build time.

The method described herein of rotating the build platform allows for a larger surface area to be exposed to the electromagnetic radiation used to solidify the deposited photocurable materials resulting in constructing of objects that are larger than the physical dimensions of individual solidification areas, thus allowing the construction of larger objects. By utilizing a small area for solidification, higher resolutions and power densities can be attained by concentrating the number of solidification points to a smaller and denser region, which through rotation, can irradiate entire portions of the build area. This reduced solidification area also results in a greater concentration of radiation to targeted areas which helps to provide a close to instantaneous cure of construction materials, yielding faster construction of an object.

The method of curing or otherwise solidifying material between a build platform and another substrate yields greater layer height uniformity, accuracy and consistency. This method also helps prevent errors during layer creation that can result from external factors such as vibration that might have otherwise disturbed materials that were not held in place between two substrates. This translates to greater reliability of the machine with particular benefits in constructing small, ultra high resolution, components so that they can be prevented from being deformed or distorted by internal or external disturbances on the 3D build device.

The problem of part delamination seen in many prior 3D build systems can be caused by forming successive individual layers of material which are inherently structurally weak along their horizontal axis's (i.e., where subsequent layers are in contact). The combined action of forcibly and repeatedly separating the solidified material from a vat floor and inadequate adhesion between layers can result in one or more layers separating causing a failed structure build. In particular, objects that contain dramatic changes in areas of increased solidification can result in fracturing of structurally weak areas that or in highly dense regions of solidified material due to the inability of the structures to provide adequate support and structural integrity and external forces applied to it during the construction process. Increasing the build area in these locations can further exacerbate the problems described above and result in greater risk for printed object fractures via delamination. The process and devices described herein provide reduced surface adhesion between solidified materials and the transparent build and as a result preserve the integrity of delicate geometries that are constructed and enhance the ability to use speeds in the construction process.

Methods incorporating features of the present invention including selectively solidifying the construction material in a relatively small area comparable to the total construction area serve to reduce adhesion forces by minimizing the physical area that generates the adhesion. The rotational motion of the build platform serves to continually remove this adhesion force as it forms preventing adhesion force accumulation. This allows for the construction of a large area with only a small portion of the constructible area ever being subject to the adhesion of material to the substrate at any given time. The transparent substrate being composed of or being treated with non-stick materials, further reduces the effects of adhesion.

Methods which incorporate features of the present invention include rotating the build platform about and above the solidification areas, providing for an innovative method for separating cured materials from a build substrate. The circular motion generated by the rotating build platform provides a superior separation method that reduces damage to newly solidified material because less force is needed to separate or slide the solidified material off the transparent build substrate and less force is applied to the constructed part. This allows the construction of very delicate geometries that can be unsupported, small, tall, thin or isolated and that could otherwise have been damaged in the separation processes of prior art 3D build systems. The method for continuous or semi continuous construction utilizing a rotating mechanism for dispensing and solidifying of photocurable material against a build platform that gradually moves upward along a z-axis results in the creation of at least one continuous spiral or helical shaped layer. This spiral buildup of material results in the formation of an object with superior layer-to-layer strength characteristics which aides in diminishing the chance for part delamination and results in lower occurrences of failed structures.

The inverted construction process provides several benefits. In several prior art systems an object is built on a platform with a first layer on the platform and subsequent layers are added on top of the prior layers. While some prior systems may use an inverted build, in the present inverted build system, a first layer is continuously applied to a build platform and solidified. However, the first layer is also continuously removed as a solid layer from the build platform during the build process and new material is fed between the first layer and the build platform so as to adhere to the rising prior layer while being continuously removed from the build platform. It allows for solidification of a large area with a relatively shallow layer of material needed, allowing for less material being used during the process compared to the amount of material needed to fill an entire vat. The vertical and inverted construction process utilizes gravity to drain excess material from previously solidified regions. The ability to form hollow cavities within the structure is very beneficial with regards to materials savings, and producing of objects with internal geometries. The use of a material stripper and drain help to further remove excess material for recycling, thus improving the economy of the machine and preventing the unintentional curing of excess material which can allow production an object that more closely resembles an intended product and has sharper details.

However, in some embodiments relying on gravity to drain excess material from the build platform may not be sufficient. As the viscosity of the build material increases the speed at which that material will flow under gravity decreases. Further, as the efficiency of the 3D build system and its components are improved the speed at which layers of build material can be laid down and solidified increases to the point where flow of the excess build material solely my gravitation may not be adequate. For example, as the intensity of the light source is increased, the frequency of the light source optimized and the chemistry of the build material is improved the combination of improvements provides more rapid solidification and the rotational speed and the build rate speed of the 3D object can be significantly increased allowing a build in layers/sec versus a current state of the art measured in layers/min. Alternatively or additionally, the viscosity of the build material may be increased as new cross-linkable polymers are developed or additives or filler materials, such as fibers or powdered metallic particles are added to or combined with the build material. Increased viscosity of the build material also results in a need for improved material delivery systems capable of uniformly delivering the higher viscosity materials. Therefore, these operational improvements, including but not limited, improved light sources, optimization of the film laydown and curing process, increased build material viscosity and increased speed of operation necessitates less reliance on gravity to remove excess material and the addition of mechanic devices to remove and recycle excess feed material from the construction/solidification are 20 which is alternatively referred to as the build zone. An added advantage of use of these techniques to remove excess materials is an increased accuracy of the dimensions of the object being built.

FIG. 23 shows an example of a suitable for adding to the inverted, spiral build 3D printing system described above, or similar configured 3D build systems. The reservoir/cartridge system 1000 provides for the storage and dispensing of high viscosity build material to the build zone and the build platform 16. The system 1000 comprises a reservoir 1002 and at least one heating element 1004 for maintaining the build material at a constant, preferably elevated temperature, to reduce the viscosity and may include one or more mixing and agitating means 1006 to aid in maintaining a relatively uniform consistency of the build material in the reservoir 1002. The agitating means 1006 shown in FIG. 23 comprises an external device for delivering ultrasonic energy to the lower external wall of the reservoir 1002. However, one skilled in the art will recognize that the ultrasonic energy source can be alternatively positioned surrounding the external vertical wall of the reservoir 1002 or other stirring/mixing devices can be used. The reservoir 1002 is constructed of a material that is inert to the 3D build material and can withstand compressive forces applied to the interior of the reservoir or the build material in the reservoir to deliver the reservoir contents.

Alternatively, as shown in FIG. 23 the cartridge 1002 can include an internal piston 1008 which can be driven by an externally supplied driving force 1010 such as from a compressor or compressed gas source. The mechanism 1010 used to drive the piston includes means to regulate the driving force fed through the pressure supply line 1022 which in turn controls the feed rate of the build material from the reservoir/cartridge system 1000, such as valves and/or a control system 1024. As shown in FIG. 23 the internal dimensions of the reservoir are chosen so that the full contents of the reservoir is expelled when the piston reaches the bottom of the reservoir 1002. In a preferred embodiment the reservoir/cartridge system 1000 also includes a sensor 1012 to monitor the amount of build material remaining in the reservoir 1002. FIG. 23 shows the reservoir 1002 mounted within a frame or holder 1014 with a lower opening connected to a coupling 1016 which is then connected to a flow control valve 1018 for further controlling the build material delivery rate. If mounted externally the feed line 1020 delivers the pressurized and heated build material to the material to a pressurized material storage area 22. Alternatively, the reservoir/cartridge system 1000 can be mounted within the base of the 3D printer system in place of the cartridge/reservoir 24 for direct delivery of the build material to the construction/solidification area 20. A further valving system (not shown) may also be included to allow refilling of the reservoir with recycled build material or to allow for adding additional build material to the reservoir 1002. Alternatively, the system may include two reservoir/cartridges 1002 with valving to allow switching from an empty to a full reservoir and allowing removal of, and replacement of, the empty reservoir 1002.

While a compressor is shown schematically as providing the externally supplied driving force 1010, various alternative systems can be used to pressurize the build material in the reservoir and to drive the piston 1008. Alternative systems include pneumatic or hydraulic systems with a compressor pressurizing the pneumatic or hydraulic systems. As a further alternative, mechanical pumps with feedback control systems for adjustment and control of the delivery mechanism can be used to regulate the pressure and flow rates of the build material.

FIG. 24 shows a further alternative storage and delivery system 1030 which uses a motor 1040 to drive a threaded shaft 1032. The shaft 1032 passes through and external bearing 1036 and a force transducer 1034 mounted to the top of the of the delivery system 1030 and a threaded collar 1038 at the top of the reservoir 1002. The motor 1040 causes the shaft to rotate and, by interacting with the internal threads in the collar 1038 move the piston 1008 downward so as force the build material through the feed line 1020 and into the build zone.

The storage, pumping systems and feed lines are all preferentially within a heated, temperature controlled space so that the viscosity of the build material can be reduced. In a further arrangement, because higher viscosity materials can have thixotropic characteristics (have time-dependent shear thinning properties) the build material is preferably kept in constant motion through the use of storage chambers and flow control valves.

The delivery of the build material is controlled (metered) to regulate the material flow to dispense build material at a rate that closely matches (satisfies) the consumption rate of the build material as dictated by the rotational speed of the components in the build zone. Due to the nature of a rotating system the angular velocity increases as the radius/diameter of build plate and the object being built on the build plate increases. Preferentially, the flow control system supplies the appropriate amount of feed material along the radius/diameter of the build. The dispensing system is designed to flow, extrude, and dispense material in a controllable manner at as close to the quantity of material required based on the layer height and width of the object being constructed. The more precise the amount material supplied matches the material needed the less excess material needs to be recovered. Additionally, slice data can be shared with the pump or feed control mechanism so as to change the amount of material dispensed along the radius to match the volume and location of material that is to be solidified on the exposure zone 118 of the cure window. This then controls the material dispensed or not dispensed at each point along segments of the cure window as may be needed to create the desired geometry in the curing of the build material forming the 3D object being constructed.

FIG. 25 shows a top perspective view of an alternative material dispensing system and construction/solidification area 1050 similar in function to the construction/solidification area 20 and the material storage area 22 but specifically designed for handling higher viscosity materials and/or excess materials deposited built zone but not readily removed by gravitational flow, particularly as the system is configured to operate at higher rational speeds, for example due to more effective and rapid curing of the build material. FIGS. 9, 10, 11, 12A and 12B show dispensing and exposure/cure zone 118 in earlier described embodiments. The construction/solidification area 1050 shown in FIG. 25 also includes a recovery and removal mechanism 1052 adjacent to an exposure/cure zone 118. For simplicity only one unit comprising a material dispenser 180 and exposure/cure zone 118 along only one radius is shown in FIG. 25. While more dispensing areas can be used, the single dispensing area shown can comprise a singular orifice (slit, hole, nozzle) or a plurality of same for controlled flow of material. The rate of material dispensed is controlled, for example by valving, flow regulation devices or using a dispenser as shown in FIG. 23 or 24 including flow control mechanisms as described above. Such a delivery system is shown schematic in FIG. 25 as a dispensing system 1054 which operates in cooperation with feed and return lines 1058 for delivering and recovering uncured build material. However, delivery, recovery and reuse of the uncured build material is not limited to these flow control and delivery mechanisms. For example, other arrangements can be used such as:

-   -   a. Vane pump system used as a metering device for controlled         delivery of material to the build area. For example, a vane pump         can employ a conical impeller and pump body where The included         angle of the conical impeller and the rotational speed of the         cone can be adjusted to provide the desired rate of flow that a         given build plate diameter would require;     -   b. a channel system comprised of varying sized outlets;     -   c. at least one flow/rate control valve; or     -   d. a number orifices and nozzles, and the location and size of         discrete dispensing orifices or nozzles being configured to flow         the appropriate amount of material to the build zone.

The excess material recovery system can, for example, comprise a doctor blade, brush or comb, a drainage system that can include a vacuum assist, an air blade or a sprayable liquid or a combination of one or more of such mechanisms. The embodiment shown in FIG. 25, and in an enlarged view in FIG. 26 of the circled portion of FIG. 25, uses as the recovery and removal mechanism 1052 one or more rotating or vibrating brushes 1053 or rotating doctor blades (not shown) that can be in a spiraled configuration on a shaft. In a preferred embodiment such as shown in FIG. 26 uses counter rotating brushes 1053 which can be adjacent to the curing zone 118 or across the center of the construction zone, the recovery system moving the uncured build material to a designated recovery area (not shown) separated from the build zone. Brushes can have the bristles 1060 thereof distributed in a helical or spiral configuration to minimize voids in the contact area between the bristles 1060 and the constructed area. This maximizes recovery of unsolidified material for a broad range of end product print geometries.

Multiple types of bristles 1060 and different bristle materials may be employed in different rollers or in the same roller. Varying characteristics of the bristle 1060 can include but are not limited to thickness, length, material type, coating type, cross sectional shape, porosity and hydrophobic/hydrophilic properties. Additionally, a comb or other brush cleaning device (not shown) can be used to remove material from the brushes 1053 or bristles 1060 so that the building material collected by the brushes 1053 or bristles 1060 is not redeposit on the construction area or object being built. Unsolidified material collected by the brushes is thus stripped from the brush bristles and directed toward a collection area.

A feed system to evacuate material collected from the rotating brush system can also be provided. This material can be recycled into a secondary material reservoir, back into the original reservoir or directed back into the main dispensing circuit and redeposited into the vat. Valves and flow controls can be used to manage and direct the recycled materials. Feed mechanisms to collect and move the collected material can, for example include, but are not limited to, augers or reciprocating pistons.

FIG. 27 is a top view and FIG. 28 a perspective top view of an alternative means to feed the viscous build material to the build and curing portion of a 3D printing system such as described herein. Such an arrangement can be used for the delivery and curing of higher viscosity build materials or simultaneously or substantially simultaneously delivering multiple different build materials, or the same build material containing, for example, different coloring agents, additives, or particles, such as metal, magnetic, or x-ray detectable particles, for the formation of a 3D object comprising a combination of materials, different coloring or inclusions for monitoring or identification purposes The build zone can comprise a build platform 1080, which is also referred to as a vat, with multiple conical or cylindrical shaped rotating brushes 1082 mounted within a frame 1086 extending along the radius of the vat, each rotating brush having its independent drive motor 1084. The apparatus shown in FIG. 27 has a raised edge 1059 to retain any uncured build material not incorporated in the 3D object being constructed. The frame 1086 includes slits or holes to feed the build material to a receiving area and in turn to the rotating brushes 1082 and then to the build platform 1080.

The arrangement as shown in FIGS. 27 and 28 also includes in the area between each brush structure 1090 and adjacent to the brush structure 1090 (but not shown in FIG. 27) cure zones 180, such as shown in FIG. 25. Also, not shown are a flexible wiper/barriers and/or other excess material removal system such as a rotating brush to drain and remove excess material from the build platform 1080 and to retain any uncollected build materials as described above and shown in FIGS. 25 and 26.

The dimensions and rotational speed of each bush is selected and controlled to provide build material at a rate to match the rotation speed of the build platform 1080, and also to take into consideration the level of crosslinking energy provided through the curing zone—and rate of crosslinking of the build material.

A further method for the controlled dispensing of build materials, which can be either a liquid or powder, is using a photoreactive conical or cylindrical drum, for example arranged for example in the manner as shown for the brushes in FIGS. 27 and 28. Prior art describes uses of such photoreactive drums in laser printers for applying toner to a substrate. A laser is used to activate or excite locations on the drum creating a static charge that then attracts an oppositely charged printing material, or in the present instance a 3D printing build material. The conical or cylindrical shape and rotation speed of the drum is controlled to dispense material at a rate to match the rotational speed of the build platform 1180 to deposit the build material onto the build platform or the previously solidified layers of build material.

This method has certain advantages over other dispensing systems in that excess material is not fed onto the build platform or into the vat or a portion of the vat, eliminating or significantly reducing the no need to isolate, remove and recycle excess material. This arrangement deposits the exact amount of material needed thus reducing the complexity of the system which otherwise would require isolating and recycling excess material.

Another advantage is that by using a photoreactive drum to precisely deposit (transfer) build material onto the build platform or previous layers is that the use of a simpler, higher power light source such as a bank of UV LEDs can be used to cure or solidify the material after it is deposited. Otherwise, a high precision directed light source such as a laser or projection system is needed to selectively solidify build materials as the entire build plate is coated to create structures. Because the material is deposited only where it needs to be, a cheaper more powerful solid state light source can be used to induce solidification, resulting in faster printing. As an example, using a powdered UV curable material, the photostatic drum could be charged with an IR or near IR laser to have an opposite charge from the powdered material and as the drum rotates it will attract and pick up the powdered UV curable material. A heating element can also be used to then liquify the powder temporarily to have it adhere to the build plate or previous layers.

The conical drums also provide the option to create blends of liquids and/or powder materials, where one electrostatic roller can dispense a liquid and a second can be used to deposit a powder onto the liquid or partially cured liquid so as to provide a broad range of material combinations and reducing the need to dispense a single higher viscosity material comprising a blend of both liquid and solid components.

One or more of the conical or cylindrical drums such as shown in FIGS. 27 and 28 can be replaced by or supplemented with conical brushes, or combs to remove any excess material from the build plate and previous layers. With reference to the build platform, one such embodiment can have a conical dispensing system followed, by a solidification system (for example composed of UV, IR, near IR controlled light sources/lasers, galvanometer, or rotating polygon mirrors, projectors, or individually addressable led or laser arrays) followed by a conical brush and material collection reservoir system to remove any excess material from the build platform and/or previous layers and to also help to create a barrier for isolating build materials on the build surface from the cured material.

The method of utilizing rotational movement for construction, instead of lateral back and forth motion, as referred as oscillation, provides for increased scalability of the machine. Unlike oscillation, rotational elements that are in continuous motion in one direction do not have compensate for momentum resulting from the oscillating movement. Therefore, a machine that utilizes the described rotational technique can comprise larger and heavier components that would otherwise have significant negative impact on the construction process and operational speed. In this rotational method of construction speed is independent of construction volume. Increasing the size of the construction mechanism and the build platform will result in a greater possible build volume, translating to comparatively faster construction from a given volume of material.

Embodiments of the invention are described herein with reference to different views and schematic illustrations of idealized embodiments of the invention. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances are expected. Embodiments of the invention should not be construed as limited to the particular shapes of the regions illustrated herein but are contemplated to include deviations in shapes that result, for example, from manufacturing.

While devices, systems and methods incorporating features of the present invention are primarily directed to stereolithographic processes using liquid-based building materials. The techniques of the present invention can have application using other flowable materials and appropriate solidification technologies such as selective laser sintering (SLS), for the purposes of enhancing resolution, faster construction times, economic material use and the ability to form hollow cavities in a constructed object that would otherwise be filled with excess construction materials. Such an embodiment can utilize heated construction materials which are then solidified. The use of a laser diode that emits radiation in the infrared spectrum a construction substrate also transparent to infrared radiation. Thermal and atmospherically control over the material and build chamber 21 is desirable for greater control over the reacting materials in the construction process.

Sintered materials such as metals or powdered polymers can be used with the above process along with a heating and/or radiation source for thermal heating and/or fusing of material. Main differences from the above recited processes can be the possible addition of an atmospheric control system that would fill the build chamber 21 with an inert gas like argon or nitrogen and a thermal control system like infrared heaters. Laser beams can be used to melt and fuse the construction material.

Flowable sinterable materials or additives can also be used as, or as part of, the construction material. The sinterable materials can then be bound in place by the curing of surrounding photopolymers or the melting or binding of a powdered polymers resulting in production of a “green object.” This green object then requires the additional steps for converting the green object to create higher part densities, known as post furnace processing which can include debinding which comprises placing the part in a furnace at a temperature that vaporizes or carbonized the binding material and promotes a controlled shrinkage or necking of the green build material to hold its shape while forming a solid structure.

Infiltration, which is a process for infusing the formed solid but porous part with another material, filling in the porous voids in the part. This infused material can have a lower melting point then the main construction material. An example of one such material suitable for infiltration is copper. Molten copper can diffuse into iron powder particles creating swelling. By controlling the copper concentration, it is possible to offset the natural shrinkage of iron during sintering to help preserve part dimensions of the green object. Such a process can also be used to form structures from bio-compatible materials which can then be infused with other biomaterials to form biologically compatible implant structures.

Consolidation is a process which can occur during sintering, results in the product shrinking so as to increase the part density.

With the inclusion of a laser of sufficient power, direct thermal sintering of the construction materials or a concentration of additives contained in a dispensed formulation whose components are capable of fusion to each other and the build platform is possible. This embodiment needs greater thermal control of the material and build chamber 21 as well as a means for regulating the atmosphere which would utilize blanketing of the solidification area with inert gases such as nitrogen and argon and a method for removing any gaseous byproducts.

Examples of sinterable additives are: 17-4 and 15-5 stainless steel, maraging steel, cobalt chromium, Inconel 625 and 718, titanium Ti6Alv4, titanium Ti64, Cobalt Chrome Alloy Co28Cr6Mo, Nickel Alloy In718 Theoretically, almost any alloy metal can be used in this process. Sintering typically involves induced binding, liquid phase sintering and/or full melting. These techniques are known in the art.

FIG. 29 shows a further embodiment where the build platform 16 and build plate 18 (see FIG. 1) is replaced by a build plate 1202 mounted on the bottom of a rotational platform 1204 which is in turn mounted on a multi-axis Z height robotic arm 1200. With reference to FIG. 1. This would eliminate and provide the same function as the z-axis elevator stage 14. However, the build material storage 22, the construction/solidification area and one or more of the various alternative material dispensing systems would still be present. By utilizing a free standing separate Z axis robotic arm, which provides additional dimension of movement, the build plate is able to be positioned separate from the construction zone/vat. When a multiple material feed as described above is considered, which would have various pie shaped or other orientation segmentation, a small section in the center may be used to prevent adjacent materials from mixing and it might be difficult to print in the center. With the rotating build plate being mounted on a robotic arm it could position the center of the build plate over a specific material for any given layer while still allowing for multiple material printing. Additionally the robotic arm would allow more operating flexibility in an automate the printing processes because the build plate could be automatically removed and replaced with a new build plate after printing of the 3D object is completed.

The build plate or platform is positioned above the construction area, such that the build material delivered to the construction area forms a solidified film of the solidifyable material in the space between the exposure zone in the build area and a lower surface of the build platform. The solidified film attaches to the build platform or prior layers of solidified film on the build platform.

The build platform is mounted on an operative end of a free standing robotic Z-arm, a lower face of said build platform being positioned in a horizontal plane above and substantially parallel to an upper face of the construction area, such that the build plate has a center point along a vertical axis through a center point of the construction zone.

FIGS. 19-21 show a process flow diagram, which can incorporate computer software, for utilizing 3D printing devices incorporating features of the present invention. Regarding FIG. 19, which shows a user-initiated process 800, the session is started in an initiation step 802, which can include the initiation of software, such as OM (an Omicron Compiler File) software or other suitable software. A user can engage in and initiate a series of interrelated user actions. For example, a use can activate an import step 804, wherein the user imports 3D geometry, for example, from existing data or from recently scanned data. From this step, the user can elect to initiate a save step 806, in which the user can save the 3D geometry data, for example, an .OM software file. Alternatively, or in addition to initiating a save step 806, a user can initiate a manual re-size/reposition step 808 of the imported 3D geometry data. The 3D geometry data can then be automatically re-sized/repositioned in an automated adjustment step 810.

At any point, an existing file, for example, an existing .OM file saved in the save step 806 or a manually and automatically adjusted file from the manual and automatic adjustment steps 808, 810 can be loaded into the memory of a user interface in a load step 812. From the load step 812, several additional steps can be initiated. For example, a user can initiate a duplication step 814, wherein one or more aspects of the 3D geometry data can be duplicated. A user can then initiate an application step 816, wherein a user can alter and/or apply colors and other material options to the 3D geometric data. The user can then initiate a connection step 818, wherein the user can locate a local 3D printer and connect, after which the user can initiate a print step 820, wherein the 3D object begins to print.

During the setup process and compiling the print instructions for printing the 3D object in the print step 820, instructions can be provided to produce a solid or a hollow structure and additional steps can be initiated to further define the object. A user can initiate a hollowing step 822, whereby a hollow object is produced instead from, and instead of, an existing solid object. A user can then initiate a hollowness adjustment step 824, whereby the wall thickness of hollow or shelled products can be adjusted. An automated infill step 826 can also be initiated, wherein infill for hollow models is automatically generated. Finally, a user can initiate a customization step 828, wherein additional customized print-specific settings are applied to the 3D object.

It is understood that while the examples cited above specifically refer to .OM files, other software file formats can be utilized. For example, users can import 3D models formatted as AMF, STL, PLY<OBJ, or any other similar file known in the art. Support for auto-detecting colors and/or materials can be included. Each piece of unique imported 3D geometry data can be stored along with the transformation matrix (applied from the origin) and metadata describing color and material selections.

Referring now to FIG. 20, which shows a further process flow diagram 850 incorporating features of the present invention, an automated print preparation (scan) process 852 is initiated by the user or in response to a stimulus, for example, the printer being powered on or receiving a connection signal from a computer or other user interface. In a first step 854, intelligent mesh consolidation of an object being reproduced takes place. In some embodiments, an algorithm is utilized to consolidate all meshes in preparation for slicing. This first step 854 can be used in the production of separate combined meshes each organized by color and material. In a second step 856, the algorithm can, if necessary, automatically generate and add any support structures needed for each combined mesh. In a third step 858, radial slicing of the mesh can occur. In this step 858 one or more algorithms can radially slice the input mesh and produce encoded vector data describing the intended structure to be printed in real-world dimensions utilizing real-world units. This data can be stored and later compiled to machine-specific instructions. Layer height is taken into account at this stage and can be pre-set as a constant value for the entire print or vary throughout the print.

In a fourth step 860, the print job is compiled by one or more algorithms to produce a single compiled (machine-specific) print job file containing all the print information utilized by the printer. In a fifth step 862, this compiled print job file, which can be machine specific and can be in .OM format, is transferred to the printer.

Referring now to FIG. 21, which shows an example of a process flow 880 after a step 882 wherein the print-job file is compiled and transferred to a printer (which can be a continuation of the fifth step 862 in FIG. 20 or proceed directly from a loaded externally or independent provided print file). In a first step 884, an algorithm translates vector instructions from real-world units into a binary arrangement (arrays of individual ones and zeroes) that is used by the printer. In a second step 886, the print processor of the printer streams data bits to the curing mechanism at a hardware-synchronized rate that coincides with the motor/mirror movement. In a third step 888, the actual Heliolithography™ (curing) process occurs, utilizing continuous computer-controlled selective solidification. In a fourth step 890, a completed physical object mirroring the virtual 3D geometry is produced. 

I claim:
 1. An improved device for three-dimensional (3D) printing of structures in a vertical orientation, where the 3D printing device comprises: a construction frame, a material dispenser for delivering a flowable build material, said build material being solidifiable, a construction area and a separate build platform, both positioned horizontally within said construction frame and configured for inverted build of a solidified 3D structure there between, said build platform spaced from said construction area a defined distance and continuously moveable vertically within, and configured to rotate in a continuous or semi-continuous manner, within said construction frame so as to provide a continuously increasing or stepwise increasing defined distance between said build platform and said construction area in each 360° rotation of said build platform, the material dispenser configured to deliver a film of the flowable build material onto an exposure zone of an upper surface of the construction area, and a solidification mechanism positioned to selectively deliver a solidifying medium to the flowable build material located on the exposure zone to convert selective portions of the flowable build material into a now-flowable film retained by the build platform said build platform configured to receive and retain said non-flowable film of build material deposited onto an upper surface of the exposure zone of the construction area as the film of flowable build material solidifies and the build platform is moved said defined distance vertically upward as the build platform rotates within the construction frame, wherein, the improved device comprising a mechanical system for removing excess flowable build material from the construction area.
 2. The 3D printing device of claim 1, wherein the mechanical system for removing excess flowable build material from the construction area comprises one or more rotating or vibrating brushes or doctor blades mounted on a motor driven shaft extending at least along a radius of the construction area, the rotating or vibrating brushes or doctor blades configured to collect and move the excess flowable build material into a collection chamber.
 3. The 3D printing device of claim 2 wherein the one or more rotating or vibrating brushes or doctor blades are mounted on the shaft in a spiraled configuration.
 4. The 3D printing device of claim 1, further comprising a material barrier to keep unsolidified build material in a predefined portion of the construction area adjacent said mechanical system for removing excess flowable build material.
 5. The 3D printing device of claim 1, wherein the material dispenser comprises one or more material reservoirs for holding and delivering the build material, each of said one or more reservoirs including a piston configured to force said build material from the reservoir through feed lines to provide controlled amounts of said build material to the construction area.
 6. The 3D printing device of claim 5, wherein said one or more material cartridges are removable, refillable and replaceable.
 7. The 3D printing device of claim 5 wherein means for controlling the flow rate of build material from the reservoir to the construction area further comprises electronically controlled valves located between the reservoir and the construction area.
 8. The 3D printing device of claim 5 wherein the piston is driven by pneumatic or hydraulic pressure or a variable speed motor.
 9. A three-dimensional (3D) printing device, comprising: a construction area a material dispenser for controlled delivery of a solidifyable liquid build material to the construction area to form a film of said build material thereon; an exposure zone on an upper surface of the construction area for receiving the film of solidifyable liquid build material, a material solidification mechanism for causing the film of liquid delivered to the exposure zone of the construction area to solidify, and a build platform positioned above the construction area, said build platform and said construction area configured for delivery of the film of solidifyable material to a space between the exposure zone and a lower surface of the build platform, the solidified film being attached to the build platform or prior layers of solidified film on the build platform, wherein the build platform is mounted on an operative end of a free standing robotic Z-arm, a lower face of said build platform being positioned in a horizontal plane substantially parallel to an upper face of the construction area, said construction area and said build platform being positioned, with a center point of the build platform being located vertical above a center point of the construction zone; wherein said build platform is configured to rotate multiple 360° turns in relationship to the construction area and continuously or semi-continuously increase, in each 360° rotation, a defined distance between the build platform such that said rotating build platform causes solidified portions of said film form a 3D structure suspended below the lower surface of the build platform.
 10. The 3D printing device of claim 9, further comprising a second material dispenser.
 11. The 3D printing device of claim 9, further comprising a mechanism for removing excess construction materials from the build platform.
 12. The 3D printing device of claim 9wh wherein the material dispenser comprising one or more material containers and delivery means for supplying and directing material from the one or more material containers.
 13. The 3D printing device of claim 30, wherein said material containers are removable and replaceable. 